PCB's cable acts as antenna

[neutrino]

I am a hardware designer of home appliances. I am doing tests of immunity to electrical fast transients (BURST) of a PCB. On board there is a microcontroller, switching power supply, relays and cables connected to other devices. During the test (at any level), the microcontroller goes to fault. Removing all I/O cables direct to other devices, the appliance works perfectly. If i approaching any cable (floating or not) near microcontroller during the test, the appliances turn off.

If i use ferrite on every cable, varistor on uC power supply, nothing changes.

What can i do??

Best regards

 

[FvM]

Gather some knowledge on EMI and redesign the board.

 

[david_samtel]

You want consider two point in your design one in Electro magnetic coupling and Electro magnetic emition . if you connect io device then problem exit mean some noise signal coupling through wire that case you want to add some ferried bead entering point of micro controller .if problem due to emition mean if wire near by the problem will happen that case use shield wire if possible other wise separate wire as long as possible from micro controller . EMI & EMC main problem in switch mode supply . in your case i think it is affecting clock circuit of your design that why controller not function correctly .if possible post the setup or schematic .